Method for displaying catalog information in an E-commerce system

ABSTRACT

Method to visualize the information related to a catalog on an processing device ( 2 ) that includes a user&#39;s interface comprising a display ( 3 ). The method includes a looking through step of a database ( 11 ) that stores an E-catalog of items that can be purchased by use of said device ( 2 ). At logic-content level the database is organized according to the hierarchical tree-type structure ( 15 ) wherein the items that can be purchased are the leaf nodes (T 1 , . . . T 5 ) of the tree and the groups of items are the intermediate nodes of the tree placed at different hierarchical levels that are higher than the hierarchical level of the leaf nodes.

This application is the national phase of International ApplicationPCT/IT2005/000588 filed on Oct. 10, 2005.

The present invention refers to a method for displaying informationabout an E-catalog on an processing device including a user's interfaceprovided with a display.

As known, further to the birth of E-commerce, the suppliers of goods andservices have developed E-catalogs that can be looked through fromremote stations, and through which potential customers can receive andvisualize information about the goods and services offered by theseller, including descriptions, images, prices and information aboutavailability.

Usually, the information taken from the E-catalogs are visualized on auser's terminal, or client terminal, remotely connected to a remoteunit, or server, which includes a database containing the catalog to belooked through. Through the client terminal—which can be for instance astandard PC or a mobile personal communication device, such as acellular phone—it is then possible to carry out the remote purchase ofan item or service listed in the E-catalog, after having examined thepieces of information extracted from the E-catalog.

In view of the ever increasing popularity of the E-commerce systems, theneed was felt to make the looking through the E-catalogs particularlyeasy for the user, so that the remote purchase procedure could becomefaster and more efficient.

This need is satisfied through a visualization method as described inthe attached claim 1 in its most general form, and in the dependentclaims in the preferred embodiments.

Further characteristics and advantages brought about by the inventionwill be better understood by reading the following detailed descriptionof the preferred embodiments of the invention, which are illustrative,and therefore are not limiting, with reference to the attached figures.As to the figures:

FIG. 1 shows a block diagram of a particularly preferred example of acomputer system through which a method according to this invention canbe implemented;

FIG. 2 shows a schematic example of the hierarchical tree structure thatcan be used to organize the data of an E-catalog;

FIG. 3 shows schematically a page as displayed on a display of a user'sterminal.

In the figures, the items that are the same or similar are identified bymeans of the same numerical references.

A preferred form of a computer system through which a method accordingto this invention can be implemented is described by reference toFIG. 1. The computer system 1 includes a data processing device 2 whichin the described particular embodiment is a personal mobilecommunication device, but this is not a limiting feature.

In a particularly preferred embodiment, the data processing device 2 is,for instance, a cellular phone. In an alternative embodiment, the dataprocessing device is a PC that can be connected to a network, or apalmtop. In yet another embodiment, the device 2 is a reader ofmultimedia/music files fitted with a communication interface forconnection to a telecommunication network.

In the following part of this description, the data processing device 2will be designated “user's terminal 2”.

The user's terminal 2 includes: a user's interface provided with agraphic display 3, data processing means 4, at least one fixed orremovable local memory 5, a communication interface 6 for the connectionof the user's terminal 2 to a telecommunication network. The preferredtype of graphic display 3 is a color LCD. As an alternative, the graphicdisplay 3 can be a monochromatic display. The graphic interface of thedisplay 3 should be preferably written in Java.

The data processing means 4 includes, for example, a processing unitdestined to process the data fed by the memory 5 or thereception/transmission interface 6. The data processing unit is alsodestined to manage and monitor the memory 5, the graphic display 3 andthe communication interface 6.

As shown schematically in FIG. 1, the computer system 1 also includes aserver 10 containing a database 11, a unit 12 for querying/managing thedatabase 11 and a communication interface 13 for the connection of theserver 10 to a telecommunication network. Such a telecommunicationnetwork, which is not shown in FIG. 1, provides a bi-directionalconnection for data exchange between the user's terminal 2 and theserver 10. Data exchange occurs through the communication interfaces 6and 13 respectively. The preferred type of network is a wireless one,but can be any other type, for instance a wired network or a hybridnetwork.

The database 11 permits an E-catalog to be memorized which includes alist of items that can be purchased by a user through the user'sterminal 2. Such items can be either goods or services. In aparticularly preferred embodiment, the items listed in the catalog areessentially digital data that can be downloaded by the user by means ofthe user's terminal 2, and which are preferably contained in a databasethat can be accessed through server 10. For instance, the data arememorized in the same database 11 that also stores the E-catalog. As analternative, the digital data are memorized in another database notshown in the figure. In a particularly preferred embodiment, suchdigital data are files with multi-media contents, e.g. audio files,image file, video files. As an alternative, the same digital data makeup computer programs, such as, for instance, games or miscellaneousutilities.

FIG. 2 shows an example of architecture that can be advantageously usedto organize the E-catalog contained in the database 11 to FIG. 1. Asshown in FIG. 2, the organization of the E-catalog at logic/contentlevel is advantageously realized through a tree-type hierarchicalstructure 15 in which the items listed in the catalog are the leaf nodesT1, . . . , T5 of the tree structure, i.e. the nodes of the treestructure 15 from where no further branches branch off. Within the treestructure 15, the leaf nodes T1, . . . , T5 are the nodes that have thelowest hierarchical level.

In the tree structure 15 of the E-catalog, the sets formed by one ormore items that are similar at logic/content level form groups of itemscorresponding to intermediate nodes A_n, V_n, Gn1-Gn3, Ar1-Ar3, Ab1-Ab2of the tree structure 15. Based on the aggregation level, higher andhigher hierarchical levels are assigned to such groups along the paththat links the leaf nodes T1, . . . , T5 to a root node R_n. At logiclevel, the latter is the group, or set, that includes all the itemslisted in the E-catalog.

In the particularly preferred embodiment in which the items in thecatalog are multi-media files, the E-catalog is organized to include forinstance two macro-groups of items corresponding to the intermediatenodes A_n, V_n, which contain all the audio-only files and all the videoand audio/video files respectively. For the sake of simplicity, fromthis point on, only the portion of the tree structure 15 related tointermediate node A_n will be described in detail in this description.This is the tree section that contains the audio-only files. These filesare, for instance, the audio files in compressed format, i.e. preferablymp3 files.

In the example in FIG. 2, the intermediate node A_n that is the whole ofthe audio files in the E-catalog, has three “child” nodes, viz. Gn1,Gn2, Gn3, which relate to groups of files in the E-catalog thatrespectively include all the catalog files assigned to music genres one,two and three. As an example, music genre one might be “Rock”, genre two“Jazz” and genre three “Pop”. Obviously, it is possible to consider atree structure 15 having a higher or lower number of music genres.

Considering again the example in FIG. 2, the intermediate nodes Gn1,Gn2, Gn3 have other branches. For the sake of simplicity only those ofintermediate node-Gn2 are shown. In particular, the consideredintermediate node has three “child” nodes, viz. Ar1, Ar2, Ar3, thatcorrespond to groups of files in the catalog that belong to the samemusic genre and which include, respectively, all the catalog files thatmay be assigned to artist one, two or three. Obviously, it will bepossible to consider

for each node corresponding to a music genre—an architecture of the treestructure 15 having a higher or lower number of intermediate “child”nodes based on the range of items in the catalog.

Still with reference to the example in FIG. 2, the intermediate nodesAr1, Ar2, Ar3 have other branches of which only those related tointermediate node Ar2 are shown for the sake of simplicity. Inparticular, intermediate node Ar2 has two “child” nodes, i.e. Ab1, Ab2,which correspond to the groups of files in the catalog related to thesame music genre and to the same artist but each of which contains onlythe catalog files listed as belonging to album one or album two by thesame artist.

Obviously, it will be possible to consider, for each node correspondingto a given artist, an architecture of the tree structure 15 having ahigher or lower number of intermediate “child” nodes based on the rangeof items in the catalog. This is done to take into account the inclusionin the catalog of music files related to an artist and contained in manyor few more or albums.

Eventually, as shown in FIG. 2, also the intermediate nodes Ab1, Ab2have additional branches. In this respect, only those related tointermediate node Ab2 are shown in the figure for the sake ofsimplicity. In particular, the intermediate node Ab2 has “child” nodesT1, . . . , T5 that are the leaf nodes of the tree structure. In thisexample each of them corresponds to a music file belonging to the albumidentified through node Ab2.

In order to summarize, in the example provided, the tree structure 15 ofthe E-catalog is characterized by the following organization/divisioncriterion:

-   -   Root node    -   Type of file (audio or video);    -   Genre;    -   Artist;    -   Album;    -   Track.

It should however be borne in mind that different organization/divisioncriteria can be used depending on the type of items listed in theE-catalog. For instance, in case the above said catalog should containaudio files only, and in case it should be awkward or impracticable togroup the items based on the music genre, a simplified tree structure 15could be used as the one the organization/division criterion applicableto which is described hereafter:

-   -   Root node    -   Artist;    -   Album;    -   Track.

In a first embodiment, the E-catalog contains a data structure for eachitem that can be purchased from the catalog. This structure includes afirst data field that identifies the item and one or more data fieldsthat contain information permitting the item position to be found in thetree structure. Besides, in a particularly advantageous embodiment inwhich the database 11 of server 10 does not only include the E-catalog,but also the same items as the catalog (which consequently are files orgroups of files), the tree structure 15 can be reconstructed startingfrom the meta-data associated to those files.

Considering again the computer system in FIG. 1, advantageously, theuser's terminal 2 is such as to retain in its memory a log including theinformation that permits the identification of the items alreadypurchased from the E-catalog by the user. For instance, this log, thatwill be called history log hereinafter, is stored in a fixed memory 5internal to the user's terminal 2, or, as an alternative, in a removablememory unit that is not shown in the figure. The latter unit can be aSIM (Subscriber Identity Module) card that can be inserted in the user'sterminal 2.

In the case of the embodiment in which the E-catalog items are filesthat can be downloaded from the server 10 to the memory 5 of the user'sterminal 2, the history log consists, advantageously, of the whole ofthe same meta-data associated to the already downloaded files andresident in the memory, or the history log can be obtained starting fromsuch meta-data.

In an alternative embodiment, the history log is kept in the memory ofthe server 10, for instance in the same database 11 that stores theE-catalog, or is a remote log with respect to user's terminal 2.

FIG. 3 shows in greater detail the display 3 of user's terminal 2, whichis essentially a user's interface for the visualization of the E-catalogon the user's terminal 2, or a device that permits E-catalog portions tobe selected.

In particular, in the method subject of this invention, the lookingthrough of the E-catalog occurs as follows:

-   -   by establishing a connection between user's terminal 2 and the        server 10;    -   by repeatedly interrogating the database 11 through the user's        terminal 2 in order to navigate in or explore a tree structure        15 of the type shown in FIG. 2. This is obtained through the        subsequent visualization of pages P on the display, which        correspond to selected portions of the tree-like structure 15.

In a particularly preferred embodiment, a page P visualized on thedisplay is arranged in a given number of lines R1, . . . , Rn on each ofwhich there can be visualized a related textual or graphic symbol S1, .. . , Sn so that the displayed P page can show a list L of textual orgraphic symbols (or elements) S1, . . . , Sn that are associated to thenodes of the tree structure that have the same hierarchical level andthat descend directly from the same parent node.

Preferably, the textual or graphic symbols S1, . . . , Sn visualized onthe display 3 provide an indication of the contents of the item groupsidentified by the nodes to which such textual or graphic symbols areassociated. This means that the symbols evolve dynamically along withnavigation. As an example only, this also means that if the visualizedpage P refers to the tree structure to FIG. 2, and the tree structure 15is being explored at hierarchical level “music genre”, the first line R1on display 3 will show a textual symbol (e.g. a word) or a graphicsymbol S1 (e.g. an icon) that provides an indication of the group ofitems in the catalog that are identified by the intermediate node Gn1.These are the items that are classed in the catalog as items belongingto the music genre associated to node Gn1. In the same vein, the secondline R2 will show a textual or graphic symbol S2 that relates to thegroup of catalog items identified by intermediate node G2, and so forth.In this case, the list L of the textual or graphic symbols will containonly three elements S1, S2, S3 (corresponding to nodes Gn1, Gn2, Gn3that are direct descendants of parent node A_n). However, should nodeA_n have a greater number of direct “child” nodes, list L, could fillall the lines of page P, or require a greater number of lines. In thelatter case, page P could become a page to be scrolled by use of ascroll bar B or similar tools.

In order to explore the E-catalog by navigating through it, it ispossible to expand one of the intermediate nodes associated to symbolsS1, . . . , Sn of the visualized list L starting from a page P in viewon the display. In this way, the visualization of a portion of the treestructure 15 that has a lower hierarchical level is obtained. As analternative it is also possible to navigate the tree structure 15 in the“upstream direction” in order to visualize a tree structure portion thathas a higher hierarchical level. For instance, if the page P in viewrefers to the tree structure to FIG. 2, and this structure is visualizedon the display at hierarchical level “music genre”, the first line R1 ofthe display will show a symbol S1 (textual or graphic) that indicatesthe content of the group of catalog items identified by intermediatenode Gn1. In the same vein, the second line R2 will show a textual orgraphic symbol that indicates the content of the group of catalog itemsidentified by the intermediate node Gn2, and so forth. In this case, thelist of textual or graphic symbols will be a list including only threeelements, viz: S1, S2, S3 (corresponding to nodes Gn1, Gn2, Gn3) thatare direct descendants of parent node A_n. At this point the user canselect to navigate in the tree structure by expanding the intermediatenode Gn2. In order to do so, the user can send a request for querying ofthe database 11 to the server 10 by clicking on symbol S2 with a cursor(or using equivalent selection tools). The request is aimed atextracting the information necessary to visualize a new page P on thedisplay 3 from the database 11. The new page will contain a list oftextual or graphic symbols S1, S2, S3 corresponding to the intermediatenodes Ar1, Ar2, Ar3.

With reference to FIG. 2, and bearing in mind the information providedin the foregoing, it is possible to infer that it is possible tonavigate in the E-catalog through subsequent querying of the database11, and so explore the tree structure starting from the root node R_nand ending at the leaf nodes T1, . . . , T5 by following, for instance,the path indicated by the arrows 20.

Advantageously, in conformance with the visualization method accordingto this invention, a comparison takes place between the informationextracted from database 11 and sent to user's terminal 2 and theinformation contained in the history log, which stores data sufficientto identify the catalog items already purchased by the user. Forinstance, if the history log is stored in the local memory of user'sterminal 2, the comparison is accomplished locally at the user'sterminal by the data processing means 4.

In the alternative embodiment in which the history log is stored in amemory that is remote with respect to the user's terminal and accessibleto the server 10 (for instance in the same database 11 that contains theE-catalog), the comparison is accomplished outside the user's terminal2, and preferably through the server 10. In this way the server 10 sendsthe user's terminal 2 data about the E-catalog that are integrated withthe information resulting from the comparison with the history log.

In a particularly advantageous embodiment, the data sent to the user'sterminal by the server 10 are documents in XML format, irrespective ofwhether the comparison is performed inside the user's terminal oroutside it.

Advantageously, in the method according to this invention, based on theresults of the comparison, the visualization of page P on the display 3is obtained by showing the textual or graphic symbols S1, S2, S3, . . ., Sn in list L with different graphic styles. The differentvisualization graphic styles are selected according to a coding systemwhich, based on the results of the comparison—as said above—prescribesthe use of the following styles on the same page P:

-   -   a first graphic style to visualize a symbol (or an element) S1,        S2, S3, . . . , Sn in list L, corresponding to an intermediate        node which represents a group in the tree structure that        includes items all of which had already been purchased by the        user (i.e. items which appear to have already been purchased by        the user according to the information contained in the history        log);    -   a second graphic style, different from the first, to visualize a        symbol (or an element) S1, S2, S3, . . . , Sn in list L that        corresponds to an intermediate node that represents a group that        does not contain any item previously purchased by the user;    -   a third graphic style, different from the first and the second        style, to visualize a symbol (or element) S1, S2, S3, . . . , Sn        in list L that corresponds to an intermediate node that        represents a group including at least one item that not yet been        purchased by the user.

In a particularly preferred embodiment, in the case of a color display3, the first, second and third graphic styles have different colors. Forinstance: the first graphic style is a textual style in a first font,but is destined to be visualized on the display by use of a first color(e.g. white); the second graphic style is a textual style in the firstfont, but is destined to be visualized on the display by use of a secondcolor (e.g. red); the third graphic style is a textual style in thefirst font, but is destined to be visualized on the display by use of athird color (e.g. grey).

In an alternative embodiment, which is appropriate in case the display 3is monochromatic, the first, second and third graphic styles are textualstyles characterized respectively by a first, second and third font thatare different from one another. For instance, in order to differentiatethe three styles, the three texts could be written using a bold type, anunderscored type and an italics type.

In the particular case of the visualization of a page P on the display3, which includes a list of symbols S1, S2, S3, . . . , Sn related tothe leaf nodes T1, . . . , T5 of the tree structure, a simpler graphiccoding criterion can be used. This criterion, based on the result of thecomparison between the data stored in the history log, and thoseextracted from the database 11, prescribes the use of the followingstyles on the same page P:

-   -   the first graphic style to visualize a symbol (or an element)        S1, S2, S3, . . . , Sn in the list L corresponding to a leaf        node T1, . . . , T5 that represents an item in the catalog that        had already been purchased by the user (i.e. an item that        appears to have been already purchased by the user according to        the information contained in the history log);    -   the second graphic style to visualize a symbol (or an element)        S1, S2, S3, . . . , Sn in the list L corresponding to a leaf        node that represents an item that had not been previously        purchased by the user.

For instance, if the items in the E-catalog are music files, each symbolS1, S2, . . . , Sn in the list can be a word corresponding to the titleof the track. And in the case of a track already purchased by the user(i.e. a track that appears to have already been purchased by the userfollowing the check of the history log) the word (symbol) will bevisualized on the display 3 in white, otherwise the visualization willbe in red.

As resulting from the above, it is pointed out that the goals definedfor this invention have been fully achieved. In particular, the methodconcerning the looking through of the E-catalog by a user is veryintuitive. Only the actually requested pieces of information aretransmitted to the user's terminal by the server, hence thevisualization of such pieces of information on a small-size display isparticularly easy. Besides, the use of the different characteristics ofthe graphic styles for the visualizations described above, which appliesstarting from the intermediate nodes, is able to guide the user duringnavigation and thus prevents the user from looking through sections ofthe catalog that contain items already purchased by him/her. In thismanner, the time required to look through the catalog is shorter, andthis results in a direct economic benefit for the user.

Obviously, a skilled in the art will be able to embody modifications andchanges in this invention to meet specific and incidental requirements,but all such modifications and changes are within the scope of theprotection of the invention, as defined in the following claims.

1. Method for displaying information related to a catalog on an dataprocessing device including a user's interface comprising a display,said method comprising the following steps: connecting the device to adatabase storing an E-catalog of items that can be purchased by a userthrough said device; the catalog being organized at logic-content levelto present a hierarchical tree structure in which the items that can bepurchased are the leaf nodes of the tree, and the groups of items areintermediate nodes of the tree placed at different hierarchical levelsthat are higher than a hierarchical level of the leaf nodes; storing ahistory log in a memory, which contains information able to permitidentification of catalog items already purchased by the user; queryingthe database through said device to visualize on said display a pagethat corresponds to a portion of the tree structure and includes a listL of textual or graphic symbols corresponding to intermediate nodes ofthe structure that have same hierarchical level and that descenddirectly from a same node of the tree structure; extractingvisualization information necessary to visualize said page from thedatabase; comparing the visualization information with said history log;visualizing said page on the display, by showing said textual or graphicsymbols through different graphic visualization styles according to agraphic coding criterion that, on the basis of the result of thecomparison step, provides adoption of: a first graphic style tovisualize a symbol in the list that corresponds to an intermediate noderepresenting a group including items already purchased by the user; asecond graphic style, different from the first graphic style, tovisualize a symbol in the list that corresponds to an intermediate noderepresenting a group that does not include any item already purchased bythe user; a third graphic style, different from the first and secondgraphic styles, to visualize a symbol of the list that corresponds to anintermediate node representing a group that includes at least one itemnot yet purchased by the user.
 2. The method according to claim 1,wherein said visualized page is a navigable page to show selectively onthe display further portions of said tree structure, and wherein saidquerying, extracting, comparing and visualizing steps are repeated forevery further portion of the tree structure to be visualized during saidnavigation.
 3. The method according to claim 1, which also includes thefollowing steps: querying of the database through said device tovisualize on said display a further page corresponding to a portion ofsaid tree structure and including a list of textual or graphic symbolsrelated to leaf nodes; extracting of additional information to visualizesaid further page from the database; comparing the extracted additionalinformation with said history log; visualization of the further page onthe display, by showing said textual or graphic symbols throughdifferent graphic visualization styles according to a graphic codingcriterion that, on the basis of the result of the comparison step,provides adoption of: said first graphic style to visualize a symbol inthe list that corresponds to a leaf node representing an item alreadypurchased by the user; said second graphic style to visualize a symbolin the list that corresponds to a leaf node representing an item not yetpurchased by the user.
 4. The method according to claim 1, wherein thedisplay is a color display and wherein said first, second and thirdgraphic styles are graphic visualization styles that use a respectivefirst, second and third color different from one another.
 5. The methodaccording to claim 4, wherein the first, second and third colors arerespectively: white, red and gray.
 6. The method according to claim 1,wherein said first, second and third graphic styles are respectively afirst, a second and a third font different from one another.
 7. Themethod according to claim 1, wherein said history log is resident in amemory contained in said device, said method also including a receivingstep of said information extracted from the database by said device, andwherein said comparing step is performed inside said device.
 8. Themethod according to claim 7, wherein said memory can be removed fromsaid device.
 9. The method according to claim 1, wherein said historylog is resident in a memory remote with respect to said device andwherein said comparing step is carried out outside said device, saidmethod also including a receiving step of the information resulting fromthe comparison by said device.
 10. The method according to claim 1,wherein the device is a mobile communication terminal.
 11. The methodaccording to claim 1, wherein the items that can be purchased aremulti-media files.
 12. The method according to claim 11, wherein saidfiles can be downloaded in a memory of said device.
 13. Acomputer-readable storage medium having stored thereoncomputer-executable instructions for displaying on a display of a dataprocessing device, information related to a catalog, by performing thesteps of: querying a database in which is stored an E-catalog of itemsthat can be purchased by a user through said device, wherein the catalogis organized at a logic-content level to present a hierarchical treestructure in which the items that can be purchased are the leaf nodes ofthe tree, and the groups of items are intermediate nodes of the treeplaced at different hierarchical levels that are higher than ahierarchical level of the leaf nodes; extracting visualizationinformation necessary to visualize a page that corresponds to a portionof the tree structure and includes a list of textual or graphic symbolscorresponding to intermediate nodes of the structure that have samehierarchical level and that descend directly from a same node of thetree structure; comparing the visualization information with a historylog that contains information able to permit identification of catalogitems already purchased by the user; and visualizing said page on thedisplay, by showing said textual or graphic symbols through differentgraphic visualization styles according to a graphic coding criterionthat, on the basis of the result of the comparison step, providesadoption of: a first graphic style to visualize a symbol in the listthat corresponds to an intermediate node representing a group includingitems already purchased by the user; a second graphic style, differentfrom the first graphic style, to visualize a symbol in the list thatcorresponds to an intermediate node representing a group that does notinclude any item already purchased by the user; and a third graphicstyle, different from the first and second graphic styles, to visualizea symbol of the list that corresponds to an intermediate noderepresenting a group that includes at least one item not yet purchasedby the user.
 14. A device for use in an E-commerce system, the devicecomprising: a graphics display; a communication interface; a localmemory that includes a history log containing identification informationof at least one item that has already been purchased by a user of thedevice, from an E-catalog of items; and a processing unit configured forexecuting program code that implements the following steps: transmittingthrough the communication interface, to a server, a query to access adatabase in which is stored the E-catalog of items that can be purchasedby the user through the device, wherein the catalog is organized at alogic-content level to present a hierarchical tree structure in whichthe items that can be purchased are the leaf nodes of the tree, and thegroups of items are intermediate nodes of the tree placed at differenthierarchical levels that are higher than a hierarchical level of theleaf nodes; extracting visualization information necessary to visualizea page that corresponds to at least a portion of the tree structure andincludes a list of textual or graphic symbols corresponding tointermediate nodes of the structure that have same hierarchical leveland that descend directly from a same node of the tree structure;comparing the visualization information with the history log stored inthe local memory; and visualizing said page on the graphics display, byshowing said textual or graphic symbols through different graphicvisualization styles according to a graphic coding criterion that, onthe basis of the result of the comparison step, provides adoption of: afirst graphic style to visualize a symbol in the list that correspondsto an intermediate node representing a group including items alreadypurchased by the user; a second graphic style, different from the firstgraphic style, to visualize a symbol in the list that corresponds to anintermediate node representing a group that does not include any itemalready purchased by the user; and a third graphic style, different fromthe first and second graphic styles, to visualize a symbol of the listthat corresponds to an intermediate node representing a group thatincludes at least one item not yet purchased by the user.